Here we describe the detection and identification of a yellow chlorophyll catabolite (Cj-YCC) in fresh extracts of senescent leaves of Cercidiphyllum japonicum. In addition, we report its partial synthesis by oxidation of Cj-NCC-1, the major (colourless) “nonfluorescent” chlorophyll catabolite (NCC) found in degreened leaves of C. japonicum. The spectroscopic analysis and structural characterization indicated Cj-YCC to be a simple dehydrogenation product of Cj-NCC-1 (by formal removal of a hydrogen atom at the C(20)- and C(1)-positions). Indeed, NCCs are easily oxidized and were first called “rusty pigments”, as they had a tendency to turn brown upon storage on a dry silica gel plate. The yellow tetrapyrroleCj-YCC may thus come about by oxidation of Cj-NCC-1 in the leaves. Its presence in the yellow leaves of a deciduous tree provides the first evidence for the contribution of a coloured chlorophyll catabolite to the fall colours.